JP7729299B2 - Semiconductor photodetector - Google Patents

Description

This disclosure relates to a semiconductor light-receiving element.

Non-Patent Document 1 discloses a photodiode having a light-receiving layer provided on an n-type indium phosphide (InP) substrate. The light-receiving layer has 150 pairs of type II superlattices. Each pair includes a gallium indium arsenide (GaInAs) layer and a gallium arsenide antimonide (GaAsSb) layer.

Rubin Sidhu, et al, "ALong-Wavelength Photodiode on InP Using Lattice-Matched GaInAs-GaAsSb Type-IIQuantum Wells" IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 17, NO. 12, DECEMBER 2005, p.2715-2717

In the above photodiode, the spectrum of the optical absorption coefficient changes significantly depending on the polarization direction of the incident light.

The present disclosure provides a semiconductor light-receiving element with a spectrum of optical absorption coefficients that has low dependence on the polarization direction of incident light.

A semiconductor light-receiving element according to one aspect of the present disclosure comprises a first III-V group semiconductor layer of a first conductivity type, a second III-V group semiconductor layer of a second conductivity type, and a light-receiving layer provided between the first III-V group semiconductor layer and the second III-V group semiconductor layer in a first direction, the light-receiving layer comprising a plurality of unit structures stacked in the first direction, each of the plurality of unit structures including a laminate and a gallium arsenide antimonide layer, the laminate comprising a first gallium arsenide layer including j gallium arsenide monolayers, a first indium arsenide layer including m indium arsenide monolayers, k laminate structures, and j-1 gallium arsenide antimonide layers. and a second gallium arsenide layer including an arsenic monolayer, wherein the second gallium arsenide layer, the k stacked structures, the first indium arsenide layer, and the first gallium arsenide layer are stacked in this order in the first direction, and each of the k stacked structures includes a third gallium arsenide layer including n gallium arsenide monolayers and a second indium arsenide layer including m indium arsenide monolayers, and in each of the k stacked structures, the second indium arsenide layer and the third gallium arsenide layer are stacked in this order in the first direction, and each of j, m, and n is an integer greater than or equal to 1, and k is an integer greater than or equal to 0.

The present disclosure provides a semiconductor light-receiving element having a spectrum of optical absorption coefficients that has low dependence on the polarization direction of incident light.

FIG. 1 is a cross-sectional view schematically showing a semiconductor light-receiving element according to an embodiment. FIG. 2 is a cross-sectional view schematically showing a light-receiving layer included in the semiconductor light-receiving element of FIG. FIG. 3 is a cross-sectional view schematically showing a unit structure included in the absorption layer of FIG. FIG. 4 is a graph showing an example of an energy band diagram in the absorption layer of the semiconductor light-receiving element according to the first experiment. FIG. 5 is a graph showing an example of an energy band diagram in the absorption layer of the semiconductor light-receiving element according to the second experiment. FIG. 6 is a graph showing an example of the spectrum of the optical absorption coefficient obtained in the first experiment. FIG. 7 is a graph showing an example of the spectrum of the light absorption coefficient obtained in the second experiment. FIG. 8 is a perspective view showing an example of the atomic arrangement in the unit structure of the first experiment. FIG. 9 is a perspective view showing an example of the atomic arrangement in the unit structure of the first experiment. FIG. 10 is a perspective view showing an example of the atomic arrangement in the unit structure of the second experiment. FIG. 11 is a perspective view showing an example of the atomic arrangement in the unit structure of the second experiment. FIG. 12 is a diagram showing examples of absorption edge wavelengths in the unit structures of the first experiment and the third to twenty-fifth experiments.

Description of the embodiments of the present disclosure
First, embodiments of the present disclosure will be listed and described.

(1) A semiconductor light-receiving element includes a first III-V group semiconductor layer of a first conductivity type, a second III-V group semiconductor layer of a second conductivity type, and a light-receiving layer provided between the first III-V group semiconductor layer and the second III-V group semiconductor layer in a first direction, the light-receiving layer including a plurality of unit structures stacked in the first direction, each of the plurality of unit structures including a laminate and a gallium arsenide antimony layer, the laminate including a first gallium arsenide layer including j gallium arsenide monolayers, a first indium arsenide layer including m indium arsenide monolayers, k laminate structures, and j-1 gallium arsenide monolayers. and a second gallium arsenide layer including n monolayers, wherein the second gallium arsenide layer, the k stacked structures, the first indium arsenide layer, and the first gallium arsenide layer are stacked in this order in the first direction, and each of the k stacked structures includes a third gallium arsenide layer including n monolayers of gallium arsenide, and a second indium arsenide layer including m monolayers of indium arsenide, and in each of the k stacked structures, the second indium arsenide layer and the third gallium arsenide layer are stacked in this order in the first direction, and each of j, m, and n is an integer greater than or equal to 1, and k is an integer greater than or equal to 0.

In the semiconductor light-receiving element described above, the stacked layers in each unit structure function as electron well layers. In the semiconductor light-receiving element described above, the spectrum of the optical absorption coefficient has a lower dependence on the polarization direction of the incident light than when the electron well layer in each unit structure consists of only a GaInAs layer. This is thought to be because the atomic arrangement is symmetrical with respect to the center position of the electron well layer in the first direction.

(2) In the above (1), the semiconductor light-receiving element may further include an indium phosphide substrate, and the first III-V group semiconductor layer may be provided between the indium phosphide substrate and the light-receiving layer in the first direction. When an arsenic composition of the gallium arsenide antimonide layer is y and a ratio of the number of gallium arsenide monolayers to the sum of the number of gallium arsenide monolayers and the number of indium arsenide monolayers in the stack is r,
0.95<y+r<1.05
In this case, the lattice distortion of the gallium arsenide antimonide layer can be reduced.

(3) In (1) or (2) above, j, m, and n may each be 6 or less.

(4) In any one of (1) to (3) above, k may be 1 or greater.

(5) In any one of (1) to (4) above, k may be 13 or less.

(6) In any one of (1) to (5) above, the arsenic composition of the gallium arsenide antimony layer may be 0.3 to 0.7.

(7) In any one of (1) to (6) above, the gallium arsenide antimony layer may include p gallium arsenide antimony monolayers, where p may be an integer from 10 to 26.

(8) In any one of (1) to (7) above, the first gallium arsenide layer, the second gallium arsenide layer, and the third gallium arsenide layer may each have a thickness of 0.2 to 1.5 nm.

(9) In any one of (1) to (8) above, the first indium arsenide layer and the second indium arsenide layer may each have a thickness of 0.2 to 1.6 nm.

(10) In any one of (1) to (9) above, the thickness of the gallium arsenide antimony layer may be 2.5 to 6.3 nm.

[Details of the embodiment of the present disclosure]
Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

FIG. 1 is a cross-sectional view schematically illustrating a semiconductor light-receiving element according to one embodiment. The semiconductor light-receiving element 10 illustrated in FIG. 1 includes a first III-V semiconductor layer 12 of a first conductivity type, a second III-V semiconductor layer 14 of a second conductivity type, and a light-receiving layer 16. The first conductivity type is, for example, n-type. The second conductivity type is opposite to the first conductivity type. The second conductivity type is, for example, p-type. The light-receiving layer 16 is undoped. The semiconductor light-receiving element 10 is, for example, a photodiode. The light-receiving layer 16 is disposed between the first III-V semiconductor layer 12 and the second III-V semiconductor layer 14 in a first direction D1. The first direction D1 is the thickness direction of the light-receiving layer 16. The first direction D1 may be a direction from the first III-V semiconductor layer 12 toward the second III-V semiconductor layer 14. The first direction D1 may be a crystal growth direction. Alternatively, the first direction D1 may be a direction from the second III-V semiconductor layer 14 toward the first III-V semiconductor layer 12. The first direction D1 may be a direction opposite to the crystal growth direction.

The first III-V semiconductor layer 12 may be an indium phosphide (InP) layer. The dopant concentration in the first III-V semiconductor layer 12 may be 1×10 ²³ to 1×10 ²⁴ m ⁻³ . The thickness of the first III-V semiconductor layer 12 may be 0.1 to 1 μm. Examples of n-type dopants include silicon (Si), tellurium (Te), and tin (Sn).

The second III-V semiconductor layer 14 may be an InP layer. The dopant concentration in the second III-V semiconductor layer 14 may be 1×10 ²³ to 1×10 ²⁴ m ⁻³ . The thickness of the second III-V semiconductor layer 14 may be 0.1 to 1 μm. Examples of p-type dopants include zinc (Zn) and beryllium (Be).

The semiconductor light-receiving element 10 may further include a substrate 18. The substrate 18 may be a III-V semiconductor substrate such as an InP substrate. The substrate 18 may be a semi-insulating substrate. In the first direction D1, the first III-V semiconductor layer 12 may be provided between the substrate 18 and the light-receiving layer 16. The first III-V semiconductor layer 12 may be provided on the primary surface of the substrate 18. The primary surface of the substrate 18 may be a {100} plane. The {100} plane includes the (100) plane, (010) plane, (001) plane, (-100) plane, (0-10) plane, and (00-1) plane. The (100) plane, (010) plane, (001) plane, (-100) plane, (0-10) plane, and (00-1) plane are equivalent to one another. The primary surface of the substrate 18 may be perpendicular to the first direction D1.

The semiconductor light receiving element 10 may further include a first conductivity type III-V semiconductor layer 20. The III-V semiconductor layer 20 is provided between the first III-V semiconductor layer 12 and the substrate 18 in the first direction D1. The III-V semiconductor layer 20 may be a contact layer. The III-V semiconductor layer 20 may be an InP layer. An electrode 30 may be connected to the III-V semiconductor layer 20.

The semiconductor light receiving element 10 may further include a second conductivity type III-V semiconductor layer 22. In the first direction D1, the second III-V semiconductor layer 14 is provided between the III-V semiconductor layer 22 and the light receiving layer 16. The III-V semiconductor layer 22 may be a contact layer. The III-V semiconductor layer 22 may be a Ga _z In _1-z As layer (also referred to as a GaInAs layer). z is the gallium (Ga) composition. z is greater than 0 and less than 1. An electrode 40 may be connected to the III-V semiconductor layer 22.

The semiconductor light receiving element 10 can detect incident light L. The incident light L may be visible light or infrared light having a wavelength of 0.4 to 3 μm. The incident light L may travel in a first direction D1. The incident light L may pass through the substrate 18 and enter the light receiving layer 16. The semiconductor light receiving element 10 may be used in a spectroscopic system, imaging system, or optical communication system of a gas analyzer.

Figure 2 is a cross-sectional view schematically illustrating the light-receiving layer included in the semiconductor light-receiving element of Figure 1. As shown in Figure 2, the light-receiving layer 16 includes a plurality of unit structures U1 stacked in a first direction D1. Adjacent unit structures U1 may be in contact with each other. The number of unit structures U1 may be 100 to 500. The plurality of unit structures U1 form a superlattice.

FIG. 3 is a cross-sectional view schematically illustrating a unit structure included in the absorption layer of FIG. 2. As shown in FIG. 3, each unit structure U1 includes a laminate LM and a gallium arsenide antimonide (GaAs _y Sb _1-y ) layer L1. The GaAs _y Sb _1-y layer L1 and the laminate LM may be laminated in this order in the first direction D1. Alternatively, the laminate LM and the GaAs _y Sb _1-y layer L1 may be laminated in this order in the first direction D1. y represents the arsenic (As) composition. y is greater than 0 and less than 1. y may be 0.3 to 0.7. In this case, the GaAs _y Sb _1-y layer L1 can be lattice-matched to the InP layer. The GaAs _y Sb _1-y layer L1 may include p GaAs _y Sb _1-y monolayers. p may be an integer from 10 to 26. A monolayer refers to a layer containing a single molecule (III-V compound semiconductor molecule) in the thickness direction. In the case of a III-V compound semiconductor having a zinc blende structure, the thickness of the monolayer is half the length of the lattice constant in the thickness direction. The thickness of the monolayer is, for example, 0.28 to 0.32 nm. The thickness of the monolayer can vary depending on the type of material, temperature, or amount of lattice distortion.

The stack LM includes a gallium arsenide (GaAs) layer L3 (first gallium arsenide layer), an indium arsenide (InAs) layer L2 (first indium arsenide layer), k stack structures LS, and a GaAs layer L4 (second gallium arsenide layer). The GaAs layer L3 includes j GaAs monolayers. The InAs layer L2 includes m InAs monolayers. The GaAs layer L4 includes j-1 GaAs monolayers. Each stack structure LS includes a GaAs layer L5 (third gallium arsenide layer) and an InAs layer L6 (second indium arsenide layer). Each stack structure LS may be a pair including a single GaAs layer L5 and a single InAs layer L6. The GaAs layer L5 includes n GaAs monolayers. The InAs layer L6 includes m InAs monolayers. The GaAs layer L4, k stacked structures LS, InAs layer L2, and GaAs layer L3 are stacked in this order in the first direction D1. In each stacked structure LS, the InAs layer L6 and GaAs layer L5 are stacked in this order in the first direction D1. In the stacked body LM, the GaAs layers and InAs layers can be stacked alternately in the first direction D1.

Each of j, m, and n is an integer greater than or equal to 1. Each of j, m, and n may be 6 or less. j and m may be the same integer or different integers. m and n may be the same integer or different integers. n and j may be the same integer or different integers. When j is 1, the laminate LM does not include the GaAs layer L4. k is an integer greater than or equal to 0. k may be greater than or equal to 1. k may be 13 or less. When k is 0, the laminate LM does not include the stack structure LS.

In the unit structure U1, the arrangement of the GaAs monolayer, the InAs monolayer, and the GaAs _y Sb _1-y monolayer can be expressed as follows:
(GaAs) _j (InAs) _m ([GaAs] _n [InAs] _m ) _k (GaAs) _j-1 (GaAs _y Sb _1-y ) _p

The arrangement order of the monolayers is the order in the direction opposite to the first direction D1. As described above, j, m, n, (j-1), and p at the bottom right of each monolayer represent the number of monolayers. k represents the number of pairs represented by ([GaAs] _n [InAs] _m ).

The InAs layer L2 may be in contact with the GaAs layer L3 and the GaAs layer L5. The InAs layer L6 may be in contact with the GaAs layer L5. The GaAs layer L4 may be in contact with the InAs layer L6 and the GaAs _y Sb _1-y layer L1. The GaAs layer L3 in one unit structure U1 may be in contact with the GaAs _y Sb _1-y layer L1 in the adjacent unit structure U1. The GaAs _y Sb _1-y layer L1 may function as an electron barrier layer or a hole well layer. The stacked body LM may function as an electron well layer or a hole barrier layer.

Each of the InAs layers L2 and L6 and the GaAs layers L3, L4, and L5 has a thickness smaller than that of the GaAs _y Sb _1-y layer L1. The thickness of the GaAs _y Sb _1-y layer L1 may be 2.5 to 6.3 nm. The thickness of each of the InAs layers L2 and L6 may be 0.2 to 1.6 nm. The thickness of each of the GaAs layers L3, L4, and L5 may be 0.2 to 1.5 nm.

When the As composition of the GaAs _y Sb _1-y layer L1 is y and the ratio of the number of GaAs monolayers to the sum of the number of GaAs monolayers and the number of InAs monolayers in the laminate LM is r, the following formula (1) may be satisfied:

0.95<y+r<1.05...(1)

When the number of GaAs monolayers in the laminate LM is N1 and the number of InAs monolayers in the laminate LM is N2, r is expressed by the following formula (2).
r=N1/(N1+N2)...(2)

N1 is expressed by the following equation (3).
N1=n×k+2j-1…(3)

N2 is expressed by the following equation (4).
N2=m×(k+1)…(4)

r may be greater than 0.4 and less than 0.6. In this case, y is greater than 0.35 and less than 0.65. This allows the lattice strain ε of the GaAs _y Sb _1-y layer L1 in the stacking plane to be greater than −1.2% and smaller than 1.1%. As a result, when the thickness of the GaAs _y Sb _1-y layer L1 is approximately 10 nm or less, good crystallinity is obtained.

In the semiconductor light-receiving element 10, the stack LM in each unit structure U1 functions as an electron well layer. In the semiconductor light-receiving element 10, the spectrum of the optical absorption coefficient has low dependence on the polarization direction of the incident light L compared to when the electron well layer in each unit structure consists only of a GaInAs layer. This is thought to be because the atomic arrangement is symmetrical with respect to the center position of the electron well layer in the first direction D1. With the semiconductor light-receiving element 10, changes in signal intensity can be suppressed even when the polarization direction of the incident light L changes.

The following describes various experiments conducted to evaluate the unit structure U1 in Figure 3. The experiments described below do not limit the scope of this disclosure.

(First Experiment)
The absorption layer of the semiconductor light-receiving element in the first experiment had the following configuration. Each unit structure in the absorption layer included a GaAs layer L3, an InAs layer L2, a GaAs layer L5, an InAs layer L6, a GaAs layer L4, and a GaAs _y Sb _1-y layer L1 (see FIG. 3). The absorption layer was stacked on the {100} plane of an InP substrate.

The number j of GaAs monolayers in the GaAs layer L3 is 2. The number m of InAs monolayers in the InAs layer L2 is 2. The number n of GaAs monolayers in the GaAs layer L5 is 2. The number m of InAs monolayers in the InAs layer L6 is 2. The number k of stacked structures LS is 3. The number j-1 of GaAs monolayers in the GaAs layer L4 is 1. The As composition y of the GaAs _y Sb _1-y layer L1 is 0.49. The number p of _{GaAs y} Sb _1-y monolayers in the GaAs _y Sb _1-y layer L1 is 17.

In each unit structure in the absorption layer, the arrangement of the GaAs monolayer, the InAs monolayer, and the GaAs _y Sb _1-y monolayer can also be expressed as follows:
([GaAs] ₂ [InAs] ₂ ) ₄ (GaAs) (GaAs _0.49 Sb _0.51 ) ₁₇

(Second Experiment)
The absorption layer of the semiconductor light-receiving element in the second experiment has the following configuration. Each unit structure in the absorption layer includes a GaAs _y Sb _1-y layer and a gallium indium arsenide ( _{GaxIn 1-x} As) layer. The absorption layer is stacked on the {100} plane of an InP substrate. y is 0.51. x is 0.47. The number of _{GaxIn 1-x} As monolayers in the _{GaxIn 1-x} As layer is 17. The number of GaAs _y Sb _1-y monolayers in the GaAs _y Sb _1-y layer is 17.

(First Experimental Results)
For the absorption layers of the semiconductor light-receiving elements according to Experiments 1 and 2, the band offset energy and the square of the absolute value of the magnitude of the wave function were calculated by simulation. The results are shown in FIGS. 4 and 5.

4 and 5 are graphs showing examples of energy band diagrams in the absorption layer of the semiconductor light-receiving element according to the first and second experiments, respectively. In the graphs of FIGS. 4 and 5, the horizontal axis indicates the position of each atom in the first direction D1. The vertical axis on the left side of the graph indicates the band offset energy (eV). ECBO indicates the band offset energy of the conduction band (also called the conduction band edge) at the Γ point where the wave number is 0. EVBO indicates the band offset energy of the valence band (also called the valence band edge) at the Γ point where the wave number is 0. The vertical axis on the right side of the graph indicates the square of the absolute value of the magnitude of the wave function (arbitrary units). |ψCBM| ² indicates the square of the absolute value of the magnitude of the wave function at the conduction band edge. |ψCBM| ² is located above 0 on the right vertical axis. |ψVBM| ² indicates the square of the absolute value of the magnitude of the wave function at the valence band edge. |ψVBM| ² is located below the value 0 on the right vertical axis.

As shown in Figures 4 and 5, the energy bands and wave functions in the electron well layer are different between the first and second experiments.

(Second Experimental Results)
For the absorption layers of the semiconductor light receiving elements in the first and second experiments, the spectra of the optical absorption coefficients at an operating temperature of 200 K were calculated by simulation. Incident light L travels in a first direction D1 perpendicular to the (001) plane (see FIG. 1). The results are shown in FIGS. 6 and 7.

6 and 7 are graphs showing example spectra of the optical absorption coefficient obtained in the first and second experiments, respectively. In the graphs of FIGS. 6 and 7, the vertical axis represents the optical absorption coefficient (cm ⁻¹ ). The horizontal axis represents the wavelength (μm). The solid line represents the spectrum when the polarization direction of the incident light L is the [100] direction. The dashed line represents the spectrum when the polarization direction of the incident light L is the [110] direction. The dash-dotted line represents the spectrum when the polarization direction of the incident light L is the [1-10] direction.

As shown in Figure 6, in the first experiment, the spectrum of the optical absorption coefficient hardly changed even when the polarization direction of the incident light L was changed. On the other hand, as shown in Figure 7, in the second experiment, the spectrum of the optical absorption coefficient changed significantly when the polarization direction of the incident light L was changed. Therefore, it can be seen that in the first experiment, the spectrum of the optical absorption coefficient has a lower dependency on the polarization direction of the incident light than in the second experiment. The mechanism by which the dependency on the polarization direction is reduced is explained below.

8 and 9 are perspective views showing examples of atomic arrangements in the unit structure of the first experiment. In FIGS. 8 and 9, the [001] direction is the crystal growth direction, i.e., the first direction D1 in FIG. 3. In FIG. 8, the upward direction is the [110] direction. On the other hand, in FIG. 9, the upward direction is the [1-10] direction. In FIGS. 8 and 9, ML indicates a monolayer. In actuality, either an arsenic (As) atom or an antimony (Sb) atom is arranged at the atomic site As _y Sb _1-y . In a plane perpendicular to the crystal growth direction, the As atoms and the Sb atoms are arranged at a ratio of y:(1-y) in terms of the number of atoms. Therefore, it can be considered that a virtual cation atom (As _y Sb _1-y ) having the properties of this ratio is arranged at the atomic site As _y Sb _1-y .

8, the number of interatomic bonds having a component in the [110] direction was calculated. The numbers of Ga—As bonds, In—As bonds, and Ga—(As _y Sb _1-y ) bonds are as follows:
Ga-As bonds: 6 pieces (4×1/2+2+4×1/2)
In-As bonds: 4 (4×1/2+2)
Ga-(As _y Sb _1-y ) bonds: 6 (2+4×1/2+2)

Atomic bonds located on the surface of a rectangular cell are shared with adjacent cells, halving the number of atomic bonds.

9, the number of interatomic bonds having a component in the [1-10] direction was calculated. The numbers of Ga—As bonds, In—As bonds, and Ga—(As _y Sb _1-y ) bonds are as follows:
Ga-As bonds: 6 (2+4×1/2+2)
In-As bonds: 4 (4×1/2+2)
Ga-(As _y Sb _1-y ) bonds: 6 (4×1/2+2+4×1/2)

Therefore, in the first experiment, the number of interatomic bonds having components in the same direction with respect to an electric field polarized in the [110] direction is the same as the number of interatomic bonds having components in the same direction with respect to an electric field polarized in the [1-10] direction. Furthermore, as shown in FIG. 4, the electron well layer is disposed between the first electron barrier layer and the second electron barrier layer. The energy at the interface between the first electron barrier layer and the electron well layer is the same as the energy at the interface between the second electron barrier layer and the electron well layer. This is due to the symmetry of the atomic arrangement with respect to the center position of the electron well layer in the first direction D1. Therefore, the Ga-As bond B1 shown in FIG. 8 is equivalent to the Ga-As bond B2 shown in FIG. 9. Similarly, the Ga-(As _y Sb _1-y ) bond B3 shown in FIG. 8 is equivalent to the Ga-(As _y Sb _1-y ) bond B4 shown in FIG. 9. Therefore, the optical absorption coefficient when the polarization direction is the [110] direction is almost the same as the optical absorption coefficient when the polarization direction is the [1-10] direction. In the first experiment, the spectrum of the optical absorption coefficient has low dependence on the polarization direction of the incident light.

10 and 11 are perspective views showing examples of atomic arrangements in the unit structure of the second experiment. Gallium (Ga) atoms or indium (In) atoms are actually arranged at the atomic sites Ga _x In _1-x . In a plane perpendicular to the crystal growth direction, the Ga atoms and In atoms are arranged at a ratio of x:(1-x) in terms of the number of atoms. Therefore, it can be considered that virtual cation atoms ( _{GaxIn 1-x} ) having the properties of this ratio are arranged at the atomic sites Ga _x In _1-x .

10, the number of interatomic bonds having a component in the [110] direction was calculated. The numbers of (Ga _x In _1-x )-As bonds, Ga-(As _y Sb _1-y ) bonds, Ga-As bonds, and (Ga _x In _1-x )-(As _y Sb _1-y ) bonds are as follows:
(Ga _x In _1-x ) - As bonds: 6 (4 x 1/2 + 2 + 4 x 1/2)
Ga-(As _y Sb _1-y ) bonds: 6 (2+4×1/2+2)
Ga-As bond: 0 (Ga _x In _1-x )-(A _y Sb _1-y ) bond: 0

11, the number of interatomic bonds having components in the [1-10] direction was calculated. The numbers of (Ga _x In _1-x )-As bonds, Ga-(As _y Sb _1-y ) bonds, Ga-As bonds, and (Ga _x In _1-x )-(As _y Sb _1-y ) bonds are as follows:
(Ga _x In _1-x )-As bonds: 4 (2+4×1/2)
Ga-(As _y Sb _1-y ) bonds: 4 (4×1/2+2)
Ga-As bonds: 2 (Ga _x In _1-x )-(A _y Sb _1-y ) bonds: 2 (4×1/2)

Therefore, in the second experiment, the number of interatomic bonds with a component in the same direction as an electric field polarized in the [110] direction differs from the number of interatomic bonds with a component in the same direction as an electric field polarized in the [1-10] direction. Therefore, the optical absorption coefficient when the polarization direction is the [110] direction differs from the optical absorption coefficient when the polarization direction is the [1-10] direction. In the second experiment, the spectrum of the optical absorption coefficient is highly dependent on the polarization direction of the incident light.

(Experiments 3 to 25)
The unit structures included in the light-receiving layers of the semiconductor light-receiving elements according to the third to twenty-fifth experiments are shown in FIG.

(Third Experimental Results)
For the absorption layers of the semiconductor light receiving elements according to Experiments 1 and 3 to 25, the absorption edge wavelength λ (μm) at an operating temperature of 200 K was calculated by simulation. Here, the absorption edge wavelength (cutoff wavelength) was defined as the maximum wavelength at which the optical absorption coefficient was 1×10 ² cm ⁻¹ or greater. The results are shown in FIG. 12.

Figure 12 shows examples of absorption edge wavelengths for the unit structures of Experiments 1 and 3 to 25. As shown in Figure 12, the absorption edge wavelengths were 2.45 μm or longer in Experiments 1 and 3 to 25. In Experiments 3 to 25, as in Experiment 1, the spectrum of the optical absorption coefficient also had low dependence on the polarization direction of the incident light.

The above describes in detail preferred embodiments of the present disclosure, but the present disclosure is not limited to the above embodiments.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is defined by the claims, not by the meaning described above, and is intended to include all modifications within the meaning and scope of the claims.

DESCRIPTION OF SYMBOLS 10...Semiconductor light receiving element 12...First III-V semiconductor layer 14...Second III-V semiconductor layer 16...Light receiving layer 18...Substrate 20...III-V semiconductor layer 22...III-V semiconductor layer 30...Electrode 40...Electrode B1...Ga-As bond B2...Ga-As bond B3...Ga-(As _y Sb _1-y ) bond B4...Ga-(As _y Sb _1-y ) bond D1...First direction L...Incident light L1...GaAs _y Sb _1-y layer L2...InAs layer L3...GaAs layer L4...GaAs layer L5...GaAs layer L6...InAs layer LM...Laminated body LS...Laminated structure U1...Unit structure

Claims (10)

a first group III-V semiconductor layer of a first conductivity type;
a second group III-V semiconductor layer of a second conductivity type;
a light-receiving layer provided between the first group III-V semiconductor layer and the second group III-V semiconductor layer in a first direction;
Equipped with
the light receiving layer includes a plurality of unit structures stacked in the first direction,
each of the plurality of unit structures includes a laminate and a gallium arsenide antimonide layer;
the stacked body includes a first gallium arsenide layer including j gallium arsenide monolayers, a first indium arsenide layer including m indium arsenide monolayers, k stacked structures, and a second gallium arsenide layer including j−1 gallium arsenide monolayers, wherein the second gallium arsenide layer, the k stacked structures, the first indium arsenide layer, and the first gallium arsenide layer are stacked in this order in the first direction, and each of the k stacked structures includes a third gallium arsenide layer including n gallium arsenide monolayers, and a second indium arsenide layer including m indium arsenide monolayers, and in each of the k stacked structures, the second indium arsenide layer and the third gallium arsenide layer are stacked in this order in the first direction;
A semiconductor light receiving element, wherein j, m, and n are each an integer of 1 or more, and k is an integer of 0 or more. Further comprising an indium phosphide substrate,
the first III-V semiconductor layer is provided between the indium phosphide substrate and the absorption layer in the first direction;
When the arsenic composition of the gallium arsenide antimonide layer is y and the ratio of the number of gallium arsenide monolayers to the sum of the number of gallium arsenide monolayers and the number of indium arsenide monolayers in the stack is r,
0.95<y+r<1.05
2. The semiconductor light-receiving element according to claim 1, wherein the following is satisfied: The semiconductor light-receiving element according to claim 1 or 2, wherein j, m, and n are each 6 or less. The semiconductor light-receiving element according to claim 1 or 2, wherein k is 1 or greater. The semiconductor light-receiving element according to claim 1 or 2, wherein k is 13 or less. The semiconductor photodetector according to claim 1 or 2, wherein the arsenic composition of the gallium arsenide antimony layer is 0.3 to 0.7. the gallium arsenide antimonide layer comprises p gallium arsenide antimonide monolayers;
3. The semiconductor light-receiving element according to claim 1, wherein p is an integer of 10 to 26. The semiconductor photodetector according to claim 1 or 2, wherein the first gallium arsenide layer, the second gallium arsenide layer, and the third gallium arsenide layer each have a thickness of 0.2 to 1.5 nm. The semiconductor photodetector according to claim 1 or 2, wherein the first indium arsenide layer and the second indium arsenide layer each have a thickness of 0.2 to 1.6 nm. The semiconductor photodetector according to claim 1 or 2, wherein the thickness of the gallium arsenide antimonide layer is 2.5 to 6.3 nm.